Electronically-controlled-scanning directional antenna apparatus utilizing velocity modulation of a traveling wave tube



March 5, 1963 c. J. MILLER 3,080,523 ELECTRONICALLY-CONTROLLED-SCANNING DIRECTIONAL ANTENNA APPARATUS UTILIZING VELOCITY MODULATION OF A TRAVELING WAVE TUBE Filed April 7, 1958 2 Sheets-Sheet 1 INVENTOR Coleman J. Miller ATTORNEY 3,8,523 Patented Mar. 5, 1963 33280523 ELECTRONICALLY=CONTRQLLED-SCANNING DI- RECTIONAL ANTENNA APPARATUS UTILIZING VELOCITY MODULATION 6F A TRAVELING WAVE TUBE Coleman J. Miller, Rock Hill Beach, Md assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 7, 1958, Ser. No. 726,855 Claims. (Cl. 325-15) This invention relates to a directional antenna apparatus for transmission and/ or reception of electromagnetic waves of very-high and ultra-high frequencies, and more particularly to such antenna apparatus the directionality of which can be controlled electronically.

It is well known that, aside from mechanical actuation of an antenna, the directionality of an antenna array can be varied by controlling the phasing of the signal waves respective to the individual elements of such array. However, the practical difficulties of obtaining the desired phase shifting have severely limited the application of this principle. For example, several types of antenna have been proposed which employ mechanical arrangements for phase shifting, but such mechanical arrangements impose practical limitations with respect to provision and employment of the necessary mechanism and therefore the uses for which such antennae may be employed is somewhat limited.

In view of the. foregoing remarks, it becomes an object of the present invention to provide an improved antenna array of the above general type, the directioncontrolling phase-shifting of which is effected simply and more rapidly than has been possible heretofore.

Another object of the present invention resides in the provision of an antenna apparatus for use with high frequency waves, the directionality of which is controlled electronically.

Another object of the present invent-ion resides in the provision of antenna apparatus comprising electronic means for controlling directionality and for amplifying radio-frequency signals.

Another object of the present invention resides in the provision of electronic means in the form of an electron discharge device of the velocity modulated type which is particularly adapted to control the directionality of an antenna array and amplify the radio-frequency signals handled by such array.

A further object of the present invention resides in the provision of antenna apparatus according to any of the preceding objects, which is adapted for both transmission and reception of radio-frequency signals.

A still further object of the present invention resides in the provision of antenna apparatus according to any of the foregoing objects, the directionality of which antenna apparatus may be controlled horizontally and/ or vertically.

Other objects and advantages of the present invention will become apparent from the following description when taken in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic showing of antenna apparatus constructed according to the present invention and employing a novel traveling wave tube as adapted exclusively for transmission of radio-frequency signals;

FIG. 2 is a schematic showing of similar antenna apparatus as adapted exclusively for receiving radio-frequency signals;

FIG. 3 is a schematic showing of similar antenna apparatus as adapted both for transmission and reception ofradio-frequency signals;

l FIG. 4 is a perspective view of the novel electronicallyv 2 directed antenna apparatus as adapted for scanning either horizontally or vertically, according to its orientation;

FIG. 5 is a schematic showing of a novel electronicallydirected broadside antenna array constructed according to the present invention for scanning horizontally and/ or vertically; and

FIG. 6 is a schematic showing of an antenna apparatus embodying the invention as employing an electron discharge device of the klystron tube type.

Referring to the drawings, in which the same reference numerals indicate identical parts in the various showings, the embodiment of the invention shown in FIG. 1 cmploys a traveling wave tube 1 comprising an evacuated cylindrical tube 2 of glass or other dielectric material, an electron gun section 3 which includes indirectly heated cathode 4- and accelerating beam forming anode '5, arranged to project an electron beam axially through the main portion of the tube 2 in which is disposed transducer or slow wave circuit means, which may be in the form of a helical conductor 6 as shown, for energy exchanges between the electron beam and waves traveling in the transducer. A collector electrode 8 at the remote end of the tube 2 collects the stream of electrons in the beam passed through the interior of the helical conductor 6. A lead 9 from the cathode 4 of the electron gun section 3 is connected to the negative side of a high tension source 10. A lead 11 connects the beam forming anode 5 to a low voltage point of the source it), and, according to a structural feature of the invention, the collector electrodes is connected to the positive side of the high tension source 10 by way of suitableconductor means, such as a common ground as shown, and Scan Control Means 12. such as shown as a variable resistance means, for example, suitably associated with such source 10 to vary the electrical potential between cathode 4 and said collector electrode 8 within a certain range to thereby vary the electron beam velocity within prescribed limits for reasons which hereinafter will be made apparent.

In accord with the invention, as adapted for transmission of radio-frequency energy, the slow wave circuit means in the form of a helical conductor 6 is electrically divided into a plurality of successive units 13 each of 'which has an output circuit 14 connected to a respective antenna radiating element 15, or such output circuit 14 may be designed to radiate directly, if preferred. The first unit adjacent to the gun section 3, in transmission operation for which the showing in FIG. 1 is intended, operates in the same manner as a conventional traveling wave tube; for modulation, a radio-frequency signal is fed into an RF signal input circuit 16 at the end of such unit nearest said gun section, and the RF energy thus fed to the first of units 13 of helical conductor 6 is first attenuated as it travels therealong, due to a transfer of energy to the electron beam, and then, as the proper relationship is obtained, both the RF energy in the helix and the RF energy in the beam increase exponentially at the expense of direct current beam energy. The amplifled RF energy is extracted from the first unit 13 at its output circuit it, While the RF energy in the electron beam passes through the following unit 13 and acts as its excitation. Operation of this and succeeding units 13 is similar to the first except that the initial transfer of energy to each unit occurs from the electron beam, and the amplified RF energy is extracted from the output circuits 14 respective to such units.

If equal excitation of all antenna radiating elements 15 is desired, the gain of each unit may be controlled by making all units identical and choosing such parameters as helix length and beam coupling factor so that the energy in the electron beam at the output circuit 14 of each unit is equal to that at the input to each unit. Equal electron beam energy thus will be employed for excitation of each unit 13, which will result in equal RF energy output from each.

For other illuminations, the gain can be varied, accordingly by varying the parameters of each unit so that its output is greater or less than the output of the preceding unit, as desired.

As illustrated in FIG. 1, for transmission, the input ends of each unit following the first may be connected to absorbing loads 20, preferably disposed within the tube 2, to provide stability, where necessary, under conditions vof imperfectly matched input circuits.

In addition to amplification of RF energy in supply to a plurality of antenna radiating elements during transmission, in accord with a prime feature of this invention, the direction of the RF energy beam emanating from a series of aligned antenna radiating elements driven by the tube 1 is controlled by varying the velocity of the electron beam within such tube to change the phasing between RF signals emanating from adjacent units 13 of the helical conductor 6. This is accomplished as exemplified by varying the direct current voltage between the cathode 4 of electron gun portion 3 and the collector electrode 8 by operation of such as the Scan Control Means 12 in form of the variable resistance mean exemplified, which varies the electron beam velocity according to adjustment of such means. A phase shift of the RF signal, the degree of which phase shift is dependent upon electron beam velocity, through each of the units 13 of the helical conductor 6 results, and this phase shift between adjacent waves emanating from the respective antenna radiating elements 15 affects the direction of the composite RF energy beam formed by the combination of such waves in accord with well known principles. By proper control of the electron beam voltage, the phase shift between RF signals emanating from antenna elements 15 may be varied between 1680 degrees and 1920 degrees, for example, to

cause the RF beam to scan an angular traverse of 90 degrees for example.

It is preferred that the electron beam voltage be varied within a region in which the resultant change in electron beam velocity does not materially affect the overall efficiency of the traveling wave tube 1. i

It will be understood from the foregoing description that by varying the direct current potential across the electron beam of the tube 1 periodically, for example, the RF beam from the antenna may be made to scan automatically through a prescribed arcuate path.

FIG. 4 illustrates a physical arrangement of an antenna apparatus employing the novel traveling wave tube of FIG. 1 as suitably supported in front of a parabolic cylinder reflector 21 and adapted for direct radiation of RF energy from the successive units 13 of the helical conductor 6 by provision of such as respective horns 22 coupled to the respective output circuits 14 and directed towards such reflector. In this instance, the reflector 21 defines one dimension of the RF beam according to its orientation, while the novel traveling wave tube 1 amplifies the RF signal fed it and controls the directionality of the RF beam in the other dimension.

As adapted exclusively for receiving RF signals directively at diiferent angles, and pre-amplification of such signals ahead of a receiver (not shown), the antenna apparatus embodying the traveling wave tube of FIG. 1 may be modified essentially by connecting antenna receiving elements 23 to respective input circuits 16 of the units 13 and connecting the output circuit 14 of the last succeeding unit 13 to the receiver (not shown); absorbing loads 24, Where necessary, may be connected to the output circuits 14 of the other of the units 13to provide stability under conditions of imperfectly matched output circuits.

In operation of the novel antenna apparatus as adapted exclusively for reception of RF signals, each of the units 13 of the helical conductor 6 is excited by the RF signal input from the respective antenna receiving elements 23, this RF energy from elements 23 is mixed and added successively in the helical conductor 6, and is amplified by energy exchange with the electron beam While en route to the output circuit of the last one of such units 13.

The sensitivity of the array of aligned antenna elements 23 with respect to direction in a particular dimension will depend upon the phasing between RF signals respective to adjacent units 13, and such antenna apparatus may be madeto scan a desired arcuate path electronically by varying the velocity of the electron beam in the tube 1 by suitable variation in drive potential between the electron gun portion 3 and collector electrode 8, in man her as set forth in detail in the preceding description rela- 'tive to the showing in FIG. 1.

As adapted for both transmission and reception of RF signals, under amplification and electronic directional control, junctions of the units 13, as shown in FIG. 3, of the helical conductor 6 are connected to respective radiating-receiving antenna elements 15, 23, via respective output-input circuits 14, 16, the input circuit 16 of the first .unit 13fis connected to a transmitter 25 and the output circuit 14 of the last unit 13 is connected to a receiver 26. It will be apparent from the foregoing description that RF energy from the transmitter 25 will be amplified and radiated from the array of antenna elements 15, 23 in the form of a beam of RF energy directed according to velocity of the electron beam passing through the tube 1, and alternately, during reception, RF energy will be received by the antenna elements 15, 23 directionally according to such electron beam velocity and will be amplified en route to the receiver 26.

According to other features of the invention, antenna apparatus embodying the invention can be made to scan in two directions separately or in unison by a suitable arrangement of a plurality of traveling wave tubes 1 to form or control a broadside array as illustrated in FIG. 5. According to this concept, one traveling wave tube 1,

extending crosswise of a plurality of parallel spacedsuccessive units 13 by energy exchange with its electron beam in 'manner as aforedescribed, while each of such units 13 serves as the respective RF input source in supply to the several traveling wave tubes which it spans.

In each of the parallel-arranged traveling wave tubes 1,

the RF energy fed to its first unit 13 is propagated and amplified through its successive units 13 while supplying RF energy to RF output circuits 14 at the junctions of such units, such output circuits being coupled to an- ,tenna radiating elements (not shown) or being designed to radiate directly into space. It will be seen that by varying the voltage applied across the electron beam of the traveling wave tube 1 driving the parallel-arranged traveling Wave tubes 1, the resultant variations in its electron beam velocity will effect corresponding equal phase shifts between adjacent ones of the 'RF signal output waves emanating from the parallel-arranged tubes to thereby control the direction of the RF energy beam from such array along one dimension. This variation in electron beam voltage may be elfected through employment of Horizontal Scan Control Means 12in form of such as variable resistance means in cooperation with the high tension source 10 connected to the respective traveling wave tube 1 as described in connection with the FIG. 1 showing. 2

To provide for scanning of the RF energy beam along the opposite dimension, the electron beam voltage of each of the parallel-arranged traveling wave tubes 1 may be varied simultaneously by adjustment of Vertical Scan Control Means 27 such, for example, as variable resistance means shown, arranged to control the voltage applied from a high tension source 28 between each cathode 4 of such tubes and their respective collect-or electrodes 8. By provision of mechanical interconnection between the two Voltage varying means 12. and 2.7, for example, simult-aneous scanning along both dimensions may be effected, and by provision of such voltage varying means in form suitable for production of periodic direct current voltage variations, scanning operation of the broadside antenna array may be made automatic with respect to either or both scan dimensions.

To adapt the array of FIG. 5 for direction-controlled reception of RF signals, a second traveling wave tube 1, spanning the parallel-arranged tubes 1 (at the top as shown in FIG. 5), is provided. This second spanning tube is arranged such that input circuits to its respective units 13 are fed by the last unit 13 of the parallelarranged tubes from which the summarized and amplified RF signals emerge during reception, and the output circuit 14 of the last unit of such section spanning tube is adapted for connection to an RF receiver (not shown). The electron beam voltage of this second spanning tube is arranged to be controlled in like fashion to that of the first scanning tube having the RF input and preferably, though not necessarily, by the same Scan Control Means 12, as exemplified in the drawings.

During receiving operation of the array of FIG. 5, it will be understood from previous description that the sensitivity of this array with respect to scanning one dimension will be varied according to variation in voltage applied to the electron beam of the second or output scanning tube, While sensitivity with respect to scanning the opposite dimension will be varied according to variation in voltage simultaneously applied to the electron beams of the several parallel-arranged tubes. As in the case of transmitting use, such scanning during reception may be made automatic by periodic variations in the electron beam voltages.

While the invention has been described primarily by reference to employment of a traveling wave tube or tubes, it is to be understood that the invention may be applied in conjunction with other high frequency tubes employing current or velocity modulation, such as the klystron. Such tubes depend upon resonant cavities for coupling between the electron stream and the electromagnetic circuit and therefore lend themselves to phase shift control by variation in the velocity of the electron stream in accord with the teachings of the present invention.

In FIG. 6, there is shown in schematic form a singleline antenna array embodying the invention as adapted to employment of a klystron tube in manner equivalent to the PEG. 3 showing employing a traveling wave tube as adapted for both transmission and reception. In the present instance employing a klystron tube, the RF signal from a transmitter (not shown) will be fed to a first cavity 3-9 immediately adjacent to the electron gun section 3 of such tube to introduce modulation of the electron stream or beam transmitted axially through a plurality of spaced-apart resonant cavities 31 coupled to respective antenna radiating elements 15 each extracting amplified RF energy from such cavities. In accord with the previous description of the antenna apparatus as embodying a traveling wave tube, change in the velocity of the electron beam in the klystron tube 29 will effect a phase shift between adjacent RF waves emanating from the respective antenna radiating elements 15 to thereby control the direction of the RF beam formed by the composite of such waves. Such variation in beam voltage may be eifected in manner similar to that described and shown in connection with the apparatus of FIG. 1 as employing, for example, a Scan Control Means in form .changes and modifications that of a variable resistor associated with a high tension source 19. During reception of RF signals, the RF signals will enter the cavities 31 of the tube 29 from receiving antenna elements 23, which in practice may be the radiator antenna elements 15, and these signals as fed to cavities 31 will be added in the electron beam and transmitted to an RF output cavity 3-2 adapted for coupling to a receiver (not shown). As will be appreciated from the previous description in connection with the apparatus as employing a traveling wave tube or tubes, scanning operation of the apparatus of FIG. 6 as employing a klystron tube during reception will be effected by changing the velocity across the electron beam passing through such tube to change the phase velocity between the signals entering the several cavities 31 in accord with principles of the invention set forth hereinbefore.

While there has been described what is at present considered to be the preferred embodiment or embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention, and it is therefore aimed in the appended claims to cover .all such fall within the true spirit and scope of the invention.

I claim as my invention:

1. Antenna apparatus comprising a plurality of parallel spaced-apart electronic tubular devices each having at a common end electron gun means for forming and projecting an electron beam to a corresponding opposite end, input means for modulating the respective electron beam, and a plurality of means located along said beam in energy-coupling relationship therewith, having respective outputs for electromagnetic wave signals derived by interaction between respective ones of said plurality of means and said electron beam; means for simultaneously varying the average velocity of said electron beam in each of said devices to change the phase relationship between the electromagnetic wave signals in said output along such electron beams; a similar electronic tubular device extending transversely of said plurality of electronic tubular devices, said similar electronic tubular device having means for modulating the electron beam thereof and having the output from its plurality of means coupled to the input means of said parallel spaced-apart electronic tubular devices respectively for modulation of the electron beams therein; and means for varying the average velocity of the electron beam in such transverse electronic tubular device to vary the phase relationship of the output signal Waves between said plurality of electronic tubular device.

2. Electronically-controlled-s'canning directional an tenna apparatus comprising slow wave circuit means having an input for introduction of an elemtromagnetic wave signal to initiate excitation of traveling waves therealong and having a plurality of longitudinally spaced-apart outputs for transmission of electromagnetic signal waves in out-of-phase relationship to be radiated into space compositely in the form of a directional beam of such Waves, means including a direct current source for projecting an electron beam along the path extending longitudinally of said slow wave circuit means for modulation by the signal introduced into said input and for energy-transfer excitation of successive sections of said slow wave circuit means intermediate said outputs for duplication of such signal wave therein, and directionality control means cooperable with the aforementioned means to vary the bias of said direct current source to control the average velocity of said electron beam for varying the phase relationship between signal waves respective to said outputs while same remain stationary, whereby the direction of radiation of the composite beam of waves is controlled.

3. Electronically-controlled-scanning directional antenna apparatus comprising an elongated hollow Waveguiding means adapted to transmit electromagnetic waves therealong at axial phase velocities less than the velocity 7 of light, said wave-guiding means having a plurality of Wave signal inputs feeding into said wave-guiding means at longitudinally spaced-apart sites therealong, and a wave signal output adapted for connection to receiver means, means including a direct current source for projecting an electron beam along a beam path extending longitudinally through said wave-guiding means in receipt of energy from each of said signal inputs and transmission of such energy to said signal output, and directionality control means cooperable with the aforementioned means to vary the bias of said direct current source to control the average velocity of said electron beam for varying the phase relationship between signals respective to said inputs while same remain stationary, whereby the sensitivity of said apparatus is varied with respect to direction.

4. An electronically-controlled-scanning directional antenna device comprising means including a direct current means to vary the bias of said direct current source for varying the average velocity of said electron beam to change the phase relationship between the electromagneticwave signals in said outputs while same remain stationary, thereby controlling the directivity of the composite beam formed by such signals.

5. An electronic device comprising means including a direct current source for forming and projecting an electron beam; a plurality of means, located along said beam in energy-coupling relationship therewith, having respective inputs for admittance of electromagnetic wave signals and having a common output; and directionality control means to vary the bias of said direct current source for varying the average velocity of said electron beam to change the phase relationship between the electromagnetic Wave signals in said inputs while same remain stationary, and thereby vary the sensitivity of such device with respect to direction.

References Cited in the file of this patent UNITED STATES PATENTS 

2. ELECTRONICALLY-CONTROLLED-SCANNING DIRECTIONAL ANTENNA APPARATUS COMPRISING SLOW WAVE CIRCUIT MEANS HAVING AN INPUT FOR INTRODUCTION OF AN ELEMTROMAGNETIC WAVE SIGNAL TO INITIATE EXCITATION OF TRAVELING WAVES THEREALONG AND HAVING A PLURALITY OF LONGITUDINALLY SPACED-APART OUTPUTS FOR TRANSMISSION OF ELECTROMAGNETIC SIGNAL WAVES IN OUT-OF-PHASE RELATIONSHIP TO BE RADIATED INTO SPACE COMPOSITELY IN THE FORM OF A DIRECTIONAL BEAM OF SUCH WAVES, MEANS INCLUDING A DIRECT CURRENT SOURCE FOR PROJECTING AN ELECTRON BEAM ALONG THE PATH EXTENDING LONGITUDINALLY OF SAID SLOW WAVE CIRCUIT MEANS FOR MODULATION BY THE SIGNAL INTRODUCED INTO SAID INPUT AND FOR ENERGY-TRANSFER EXCITATION OF SUCCESSIVE SECTIONS OF SAID SLOW WAVE CIRCUIT MEANS INTERMEDIATE SAID OUTPUTS FOR DUPLICATION OF SUCH SIGNAL WAVE THEREIN, AND DIRECTIONALITY CONTROL MEANS COOPERABLE WITH THE AFOREMENTIONED MEANS TO VARY THE BIAS OF SAID DIRECT CURRENT SOURCE TO CONTROL THE AVERAGE VELOCITY OF SAID ELECTRON BEAM FOR VARYING THE PHASE RELATIONSHIP BETWEEN SIGNAL WAVES RESPECTIVE TO SAID OUTPUTS WHILE SAME REMAIN STATIONARY, WHEREBY THE DIRECTION OF RADIATION OF THE COMPOSITE BEAM OF WAVES IS CONTROLLED. 